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Three-Dimensional Basin and Fault Structure From a Detailed Seismic Velocity Model of Coachella Valley, Southern California

Ajala, Rasheed and Persaud, Patricia and Stock, Joann M. and Fuis, Gary S. and Hole, John A. and Goldman, Mark and Scheirer, Daniel (2019) Three-Dimensional Basin and Fault Structure From a Detailed Seismic Velocity Model of Coachella Valley, Southern California. Journal of Geophysical Research. Solid Earth, 124 (5). pp. 4728-4750. ISSN 2169-9313. https://resolver.caltech.edu/CaltechAUTHORS:20190412-073116409

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Abstract

The Coachella Valley in the northern Salton Trough is known to produce destructive earthquakes, making it a high seismic hazard area. Knowledge of the seismic velocity structure and geometry of the sedimentary basins and fault zones is required to improve earthquake hazard estimates in this region. We simultaneously inverted first P wave travel times from the Southern California Seismic Network (39,998 local earthquakes) and explosions (251 land/sea shots) from the 2011 Salton Seismic Imaging Project to obtain a 3‐D seismic velocity model. Earthquakes with focal depths ≤10 km were selected to focus on the upper crustal structure. Strong lateral velocity contrasts in the top ~3 km correlate well with the surface geology, including the low‐velocity (<5 km/s) sedimentary basin and the high‐velocity crystalline basement rocks outside the valley. Sediment thickness is ~4 km in the southeastern valley near the Salton Sea and decreases to <2 km at the northwestern end of the valley. Eastward thickening of sediments toward the San Andreas fault within the valley defines Coachella Valley basin asymmetry. In the Peninsular Ranges, zones of relatively high seismic velocities (~6.4 km/s) between 2‐ and 4‐km depth may be related to Late Cretaceous mylonite rocks or older inherited basement structures. Other high‐velocity domains exist in the model down to 9‐km depth and help define crustal heterogeneity. We identify a potential fault zone in Lost Horse Valley unassociated with mapped faults in Southern California from the combined interpretation of surface geology, seismicity, and lateral velocity changes in the model.


Item Type:Article
Related URLs:
URLURL TypeDescription
https://doi.org/10.1029/2018JB016260DOIArticle
ORCID:
AuthorORCID
Ajala, Rasheed0000-0001-5650-8362
Persaud, Patricia0000-0003-3462-7023
Stock, Joann M.0000-0003-4816-7865
Hole, John A.0000-0002-5349-9111
Additional Information:© 2019 American Geophysical Union. Received 21 JUN 2018; Accepted 6 APR 2019; Accepted article online 11 APR 2019. We thank three anonymous reviewers, the Editor in Chief, Uri ten Brink, and the Associate Editor, Kelly Liu, for their comments and suggestions, which significantly improved this manuscript. The SSIP was funded by the U.S. Geological Survey Multihazards Demonstration Project, and the National Science Foundation Earthscope and Margins Programs through grants OCE‐0742253 (to California Institute of Technology) and OCE‐0742263 (to Virginia Tech). This research was supported by Southern California Earthquake Center (SCEC) awards 15190 and 18074 and the U.S. Geological Survey grant G15AP00062. SCEC is funded by NSF Cooperative Agreement EAR‐1033462 and USGS Cooperative Agreement G12AC20038. The SCEC contribution number for this paper is 8269. R. A. was also financially supported by the Society of Exploration Geophysicists Foundation through the merit‐based scholarship program. We refer to the extensive acknowledgments in Rose et al. (2013) for permissions and assistance received for SSIP as a whole. The data have been archived at the IRIS DMC (ds.iris.edu/pic‐ph5/metadata/SSIP/form.php). The 3‐D velocity model as well as the derived basement and estimated Z_(2.5) surfaces important for seismic hazard assessment is available for download at our LSU research webpage (https://www.geol.lsu.edu/persaud/Data.html). All figures are plotted using the Generic Mapping Tools (Wessel et al., 2013).
Group:Seismological Laboratory
Funders:
Funding AgencyGrant Number
NSFOCE-0742253
NSFOCE-0742263
Southern California Earthquake Center (SCEC)15190
Southern California Earthquake Center (SCEC)18074
USGSG15AP00062
NSFEAR-1033462
USGSG12AC20038
Society of Exploration Geophysicists FoundationUNSPECIFIED
Subject Keywords:San Andreas fault; Coachella Valley; Salton Trough; Peninsular Ranges; Eastern Transverse Ranges; Lost Horse Valley
Other Numbering System:
Other Numbering System NameOther Numbering System ID
Southern California Earthquake Center8269
Issue or Number:5
Record Number:CaltechAUTHORS:20190412-073116409
Persistent URL:https://resolver.caltech.edu/CaltechAUTHORS:20190412-073116409
Official Citation:Ajala, R., Persaud, P., Stock, J. M., Fuis, G. S., Hole, J. A., Goldman, M., & Scheirer, D. (2019). Three‐dimensional basin and fault structure from a detailed seismic velocity model of Coachella Valley, Southern California. Journal of Geophysical Research: Solid Earth, 124, 4728–4750. https://doi.org/10.1029/2018JB016260
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:94677
Collection:CaltechAUTHORS
Deposited By: Tony Diaz
Deposited On:12 Apr 2019 14:59
Last Modified:05 Nov 2019 17:58

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